When designing, for instance, furniture, buildings and vehicles, it is important that the constituent members of the structures are durable and have good strength properties, e.g. that they have good flexural rigidity and bending strength. This requirement is often contradicted by other desirable criteria, such that they should have low weight, be worth their price, be environmentally friendly and have an attractive appearance. The criteria of low weight, low price and environmental friendliness also mean that it usually is desirable that the material consumption when manufacturing the structural members is as low as possible.
Previously, it has been difficult to combine all these desirable criteria in one and the same structural material. Traditionally used types of material, such as solid wood, chip boards, masonite, MDF, and different forms of laminates weigh a lot, are often expensive, and require a relatively large material consumption during manufacture. Metals and metal alloys have similar advantages and disadvantages. Plastics and similar polymer materials, on the other hand, are often light and cost little to produce, but exhibit lower durability and strength, are not as environmentally friendly, and usually do not have the desired appearance. Composite materials comprising, for example, carbon fibre or glass fibre are often very strong and durable, but cost a lot and do not always provide the desired aesthetic impression.
Also structural members in the form of two parallel, outer boards of a more solid material, with a lighter and less material-consuming material therebetween, have been developed. Such structural members weigh little, and sometimes cost less than more continuously solid materials, but are usually not as durable.
Accordingly, there is a desire and a need for structural members of a material which is strong, has low weight, costs little to produce, and is environmentally friendly and preferably also aesthetically pleasing.